Transit mixer for improved discharge of low slump concrete



R. W. SMITH Sept. 3, 1957 TRANSIT MIXER FOR IMPROVED DISCHARGE OF LOW SLUMP CONCRETE Filed Dec. 21, 1953 INVENTOR.

By Robin W. 5M\TH a4 ATTORNEY United States Patent TRANSIT MIXER FOR IMPROVED DISCHARGE 'OF LOW'SLUMP CONCRETE Application December 21, 1953, Serial No. 399,197

2 Claims. (Cl. 259-169) This invention relates to transit type concrete agitators and mixers and particularly to an agitator or mixer which satisfactorily discharges low slump concrete.

Low slump concrete is very sticky and is quite diflicult to discharge from the conventional agitators and mixers since it tends to stick to the drum and blades. Low slump concrete hangs on the drum until almost the top of the rotation. When the concrete falls from this point it tends to fall back into the drum instead of falling into the discharge spout. While this is particularly true of the high discharge mixers it is also true in the horizontal mixers.

The principal object of this invention is to provide an agitator or mixer which will satisfactorily discharge low slump concrete. The mixer will, of course, satisfactorily discharge high slump concrete as well.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the single embodiment shown in the drawings, in which:

Fig. 1 shows a side elevation with parts broken away of a drum incorporating my invention; and

Fig. 2 is an end view of this drum taken as indicated by line 2-2 on Fig. 1.

The drum in the drawing is of the hatch-loaded variety and is shown upwardly and rearwardly inclined in approximately the angular position it would occupy when mounted on a truck mixer of the high discharge type. The manner of mounting the drum on the truck frame is not of any importance so far as the present disclosure is concerned and the drum would be equally as well mounted on a horizontal axis if desired. The drum 10 is provided with a cut-out portion 12 in which the hatch (not shown) is provided for loading the drum at the central mixing plant. Here again, the details of the hatch construction are of no importance so far as the present invention is concerned. Two spiral T-shaped blades 14, 16 are fixed on the inside of the drum, originating at the open rear end of the drum and terminating adjacent the forward end of the drum. The T blade construction is well known in the art and greatly facilitates the mixing and discharge action.

A generally frusto-conical member 18 is mounted centrally of blades 14, 16 adjacent the open rear end of the drum. This member serves one of the functions of the charging cone well known in this art in that the member facilitates discharge of the concrete. It will be noted that member 18 is comprised of two sections each of which is a frustum of a right circular cone. The innermost section 20 has its sides substantially parallel to the sides of the drum as was customary with the prior art charging cone mentioned above. However, the angle between the sides of member 22 and its axis is greater than the angle between the sides of portion 20 and its axis. This results in a cone like structure in which the surface at the top is always downwardly and rearwardly inclined with respect to a horizontal plane.

When the drum is rotated in the discharge direction the concrete is moved rearwardly by the T blades 14, 16. In the'case'of high slump concrete the concrete leaves the rear lip of the drum at about the bottom of the drum or a short ways up the righthand side of the drum (as viewed in Fig. 2) where it falls into the discharge chute. In the past, with low slump concrete the concrete, being sticky, would tend to ride up the side of the drum as it rotated in the discharge direction until it reached about the top of the drum when it would fall onto the charging cone surface which merely carried the concrete back into the drum. In the present drum the concrete still sticks to the drum surface but when it falls on the downwardly and rearwardly inclined surface of portion 22 it tends to slide rearwardly and readily falls from its more sharply contoured surface. This results in greatly improved discharge characteristics for low slump concrete.

It will be noted that the ends of blades 14 and 16 adjacent the open rear end of the drum necessarily increase in height toward the rear of the drum in the region of the portion 22 of cone 18. This feature also facilitates discharge of the concrete since it gives a larger pushing wall at the portion of the blade which must ultimately eject the concrete from the open rear end of the drum. Therefore, this feature, coupled with the form of the cone portion 22, results in far faster discharge of concretethan has heretofore been obtainable in truck mixers. The improvement in the discharge characteristics is of considerable importance since it means spending less time at the end of the haul and permits more trips during the course of a days operation.

It will be noted that this construction results in an aperture 24 centrally of the cone member 18. This aperture can, if desired, be plugged by a removable plug which would permit of inspection of the drum contents or could be removed during the hatch loading process to serve as a vent. A rear closure could be provided to seal the space between cone 18 and the drum during transit or the cone member 18 may be modified as shown and described in my application Ser. No. 399,198 now Patent No. 2,723,112 dated Nov. 8, 1955, to increase the capacity of the drum while preventing leakage about the blades-that is, between the cone member 18 and the interior walls of the drum.

When modified as shown in my copending application, the capacity of this drum may be raised to any desired extent (providing the aperture 24 is plugged) without having leakage and without requiring any other sealing apparatus at the open rear end of the drum. It will be appreciated that the present invention relates only to the improvement of the discharge characteristics of low slump concrete and for this reason the means for sealing the open rear end of the drum or preventing spillage are not shown.

Although but one embodiment of the present invention has been illustrated and described it will be apparent to those skilled in the art that various other changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. A transit mixer comprising a frame, a drum mounted on the frame for rotation about its axis and having its rear end open for discharging the drum contents, a plurality of axially spiraled blades on the interior wall of the drum and originating at the rear end of the drum, a member mounted in said drum at the rear end of the drum and cooperating with the blades and drum to define axially spiraled rearwardly diverging open ended discharge passages between the member and the interior wall of the drum, said member including a portion which is of frusto-conical shape disposed to extend through the rear discharge opening of the drum and having its axis coincident with the axis of the drum, the conical wall of said portion of the member being inclinedrearwardly and toward the axis of the drum, the upper-portion of said conical wall portion receiving material falling from the inner surface of the overlying portion of the drum to facilitate discharge thereof from the drum.

2. The construction described in claim 1 wherein said member is hollow, and open from end to end, the rear 4 end opening being in substantial a1ignment with the axis of'rotation of the drum.

References Cited in the file of this patent UNITED STATES PATENTS 2,254,639 Andrae Sept. 2, 1941 2,285,685 Shafer June 9, 1942 2,512,603 Benson June 27, 1950 10 2,731,249 Oury Jan. 17, 1956 

